DISEASE CHARACTERISTICS: Confirmed respiratory syncytial virus (RSV) pneumonia documented by rapid antigen test (ELISA or IFA), shell vial culture of bronchoalveolar lavage specimens, or tissue antigen staining of lung biopsy sample New infiltrate on chest x-ray and at least one of the following: Cough Wheezing Dyspnea and/or tachypnea (greater than 150% of baseline) Oxygen saturation less than 90% on two occasions 1 hour apart on room air Arterial oxygen pressure less than 80 No more than 60 hours since confirmation of pneumonia by chest x-ray Received prior stem cell transplantation and meet one of the following: Between start of conditioning (preparative) regimen and day 90 after allogeneic, autologous, or syngeneic stem cell transplantation (SCT) Between days 91 and 180 after unrelated HLA mismatch-related allogeneic SCT (bone marrow, peripheral blood stem cells (PBSC), or cord blood), T-cell depleted allogeneic transplantation, or CD34 selected allogeneic PBSC transplantation Between days 91 and 180 after SCT with graft-versus-host disease requiring systemic steroids expected to continue throughout study Other pulmonary pathogens in addition to RSV allowed